I'm going the 2 year route because I already have a B.S. in a field unrelated to aviation. I'm in the same boat you are-- using GI benefits and a bit of whatever housing I can save to build time.
I know a few guys who are currently flying for regionals that went through their training the hard way right after high school. Started flying through local FBOs while getting marketing degrees from community colleges in the area. During our Jr year at a 4 year college, they were already applying for some of the smaller regionals. So I know it's possible to build the time, it's just going to take a LOT of hours instructing/surveying.
If you're looking to get in to aviation, but not as a career the GI bill has you basically covered. It should be enough to get you through to your Instrument rating but if you're looking to go beyond that, it might take more flight time than your schedule can afford especially if you're working full time elsewhere.
My two cents, the 2 year option is more practical than the 4 especially if you're trying to get the R-ATP certs. If not, just use local FBOs and instructors that work with VA benefits.